The production of certain metals, such as uranium, is typically done by the reduction of the metal fluoride salt. For example, the reaction of magnesium metal with greensalt (UF.sub.4) produces magnesium fluoride (MgF.sub.2) and uranium metal. An analogous reduction process is also used for production of beryllium metal and can further be employed in the production of practically any metal including e.g., hafnium, titanium, and zirconium. The redox products are comprised principally of a metal and an alkaline earth fluoride matrix.
The magnesium fluoride invariably emerges from the above reaction with some level of contained uranium contamination, generally exceeding about 30 pCi/g in the case of uranium metal production. The magnesium fluoride typically contains up to about 4.0 wt % uranium within the matrix which is a highly refractive, i.e., relatively insoluble matrix containing a variety of uranium chemical forms and oxidation states. Such matrix is generally classified as a low-level nuclear waste and must be disposed of at a licensed radioactive disposal site. As such, the magnesium fluoride per se, even though not a radionuclide, represents a large liability in terms of disposed costs.
The processing of magnesium fluoride waste by-products in order to extract and concentrate uranium, and to recover magnesium and fluoride values in substantially purified form for further industrial use would reduce this cost liability if the processing procedure were cost effective. Typically, however, magnesium fluoride processing techniques have involved a variety of acid digestions using both inorganic and organic types, both separately and in combination, in the attempt to dissolve the refractive matrix and release the contained metals and other values. Although a fair fraction of material can be dissolved, there still remains a substantial residue containing uranium values significantly in excess of radioactive limits established by Federal Regulations for non-radioactive waste disposal.